Google believes Dart speeds up both developers and the programs they write, but skeptics worry that it fragments Web programming and undermines the industry's focus on better JavaScript. So far, it's been a largely academic debate, but that will change in coming months.

…from my perspective we are witnessing a VHS versus Betamax moment, where the less meriting technology becomes ingrained as the defacto standard.

I wouldn't be so pessimistic. Google's javascript compilers (Dart and Closure) play up to the fact that browsers have to stay backwards compatible, so any language that efficiently can be compiled to javascript stand a chance of success.

asm.js is wasteful, typed javascript is not good enough, closure is a crutch… Dart is not as static as I like it to be, but it is good enough to make decent IDE-support possible, both when coding and when debugging. Dart is a bit too scripty, but the alternatives are worse, much worse.

Dart provides an environment with good debug functionality, well working closures, well rounded libraries etc. There are some minor syntactical issues (if you mistype a . /.. you risk getting the wrong reference assigned), but not big enough to be a show-stopper. I can't see it fail, unless Chrome fails, but then again… I could be wrong.